The Regulation Mechanism Of Kinesin-3 Family Protein KIF1A

Intracellular transport is fundamental for morphogenesis,cellular function,and survival.Kinesin superfamily proteins(KIFs)are molecular motors that can directionally transport various cargos,including membranous organelles,protein complexes and mRNAs.The motor activity should be tightly regulated to ensure that the ATP hydrolysis and processive motility occur only upon coupling to the correct cargo.In neurons,the kinesin-3 motor KIF1a can drive the transport of presynaptic vesicles and other membrane-bound organelles along microtubule tracks from cell body to axon.In this study,by using the yeast-two-hybrid experiment and GST-pull-down assay,we found that the motor domain of KIF1A can interacts with its CC2 domain.Since the motor domain of KIF1A plays a key role in its binding to microtubules,an autoinhibitory mechanism of KIF1A could be proposed,i.e.,when KIF1A is in an inactive state,the CC2 domain can interact with its motor domain and thereby prevents the binding between the motor domain and microtubules.Recent studies demonstrated that the small G protein ARL8A can promote the transport of synaptic vesicles to the axonal termini.Since KIF1A is responsible for this axonal transport,it is possible that ARL8A can activate KIF1A.In our previous studies,we found that the CC3 domain of KIF1A can interact with ARL8A.The interaction between the wild type ARL8A and KIF1A requires GTP,whereas the Q75L-ARL8A mutant can directly interact with KIF1A.In this study,we further found that the D133N-ARL8A mutant shows much stronger binding to KIF1A CC3 domain.Since the structure of the KIF1A-CC3/ARL8A complex would elucidate the molecular mechanism underlying the ARL8A-mediaetd activation of KIF1A,and the finding of the D133N-ARL8A may play a critical role for achieving this complex structure.In summary,an autoinhibitory mechanism of KIF1A was proposed in this study,which would provide a new working model for the regulation of KIF1A and the kinesin-3 family motors.The D133N-ARL8A mutant was found to bind to KIF1A much stronger,which would also help the further study on the KIF1A-CC3/ARL8A complex structure for elucidating the molecular mechanism for the ARL8A-mediaetd activation of KIF1A.